In the United States, while some telephone calls are handled by one service provider, e.g., a local call completed between wired (as opposed to wireless) telephone stations, many calls, e.g., long-distance calls, require multiple service providers to cooperate for their completion. The initial carrier providing telephone service is typically a local service provider, illustratively a local exchange carrier (LEC), such as New Jersey Bell. However, the term "local service providers", as used herein, also includes cellular (wireless), cable and any so-called "dial-tone" or "first contact service" provider. Such local service providers are also, typically, the network of last contact for a call, because they are connected to the called subscriber where the call exits the public network. Thus, in other words, for a particular call, the network of first contact and the network of last contact are those networks that are directly connected to the telephones of the caller and called party, respectively.
The network connecting the network of first contact with the network of last contact is typically, but not necessarily, that of a long-distance--or so-called interexchange (IXC)--telephone carrier. In the United States, AT&T, MCI and Sprint are three such IXCs. For example, presently, for a long-distance telephone call between wired telephone subscribers, the local service providers serving the calling and called telephones are two different LECs which are interconnected by a long-distance, or interexchange, carrier.
In some call scenarios, there are only two networks connected together, the network of first contact and the network of last contact. For example, for a local call from a wired telephone to a wireless telephone station within the same area code, the network of first contact is a LEC connected to the calling party at the wired telephone station while the network of last contact is a cellular service provider connected via a radio link to the telephone of the called party, both networks being those of local service providers. Thus, it is possible for a telecommunications carrier to serve multiple roles.